Method of and means for engine operation with cylinders selectively unfueled

ABSTRACT

A method and apparatus for controlling the supply of fuel to selected ones of the cylinders of a multi-cylinder internal combustion engine. The apparatus includes solenoid operated valves which are electrically energized to cause fuel to be supplied to the respective cylinders of the engine. Actuating current pulses are normally applied to all valves to discharge the required amount of fuel for each cylinder power stroke. In accordance with the present invention, an electronic system selectively disables certain of the solenoid operated valves to prevent fuel from being injected so as to cause the associated cylinder to pump air only. This unpowered cylinder operation may be used for any desired purpose, such as to pump air or to reduce the number of cylinders using fuel during idling or low power operation.

llttited States Patent Frost Sept. 4, 1973 SELECTIVELY UNFUELED PrimaryExaminer-Laurence M. Goodridge Assistant Examiner-Ronald B. CoxAttorney-E. W. Christen and C. R. Meland [57] ABSTRACT A method andapparatus for controlling the supply of fuel to selected ones of thecylinders of a multi-cylinder internal combustion engine. The apparatusincludes solenoid operated valves which are electrically energized tocause fuel to be supplied to the respective cylinders of the engine.Actuating current pulses are normally applied to all valves to dischargethe required amount of fuel for each cylinder power stroke. Inaccordance with the present invention, an electronic system selectivelydisables certain of the solenoid operated valves to prevent fuel frombeing injected so as to cause the associated cylinder to pump air only.This unpowered cylinder operation may be used for any desired purpose,such as to pump air or to reduce the number of cylinders using fuelduring idling or low power operation.

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ATTORNEY PATENTEDSEP 4 ma SHED 5 BF 5 INJECTION PULSE SOURCE INVENTOR.BY George 5. 5505? azmzzaw ATTORNEY V METHOD OF AND MEANS FOR ENGINEOPERATION WITH CYLINDERS SELECTIVELY UNFUELED The present inventionrelates to a method of and means for operating a multi-cylinder sparkignition internal combustion engine with one or more cylinders in anunpowered condition as desired by the operator, or in response toautomatic control.

The spark ignition internal combustion engine, such as is used commonlyon automobiles, is normally operated with fuel supplied to each of theengine cylinders. This is not necessarily the optimum operation underall conditions of engine usage. For example, the engine may under someconditions supply insufficient oxygen content in the exhaust gases toreduce unburned hydrocarbon and carbon monoxide emissions to the desiredlevels. It may thus be desirable to provide and control some form ofauxiliary air supply to provide the necessary air for this purpose inthe engine exhaust stream passing through a catalytic or otherafterburner device. Also, when an engine is operated at idle with asubstantially closed throttle, the combustion and cooling conditions arerelatively adverse. With a particular engine it may be preferable tooperate with less than all cylinders fueled and the throttle more nearlyopen at idle or low load, so that combustion takes place under morefavorable conditions.

The present invention is particularly applicable to a multi-cylinderengine, such as an eight-cylinder fourstroke engine, that operates inconjunction with a catalytic converter. In this application, asdescribed hereafter, the non-fueled cylinder operations may beprogrammed so as to provide intermittent air supply to the converterthrough the operation of unfueled power strokes in the engine itself andof the number required for effective converter operation. In accordancewith one aspect of the present invention, the catalytic memcry of thecatalyst in the converter coacts with the intermittent air supply toprovide operation comparable to that obtained with a continuous airsupply.

The present invention is further applicable to multicylinder automobiletype engines in that the non-fueled piston operations are achieved withminimum roughness imparted to the engine. In brief, the non-fueledpiston operations take place as occasional, approximately periodic,cylinder miss events having minimum effect on engine roughness and thenonly as transitory action. As the number of unpowered strokes isprogressively increased, the action corresponds more and more to aperiodic unpowered cylinder operating cycle superimposed on the normalpower strokes. The approximately equal time spacing of the unpoweredcylinder strokes minimizes the effect on engine roughness.

Further in accordance with the present invention, the action isaccommodated to a comparatively simple form of electric fuel injectionsystem, namely the type wherein the fuel injectors are energized in twoseparate groups, rather than individually for each cylinder, althoughnot limited to such a system. This typeof fuel injection has theadvantage of simplicity and consequent greater desirability, but it doesnot permit control of each injector separately from the other injectorsin the same group. One aspect of the present invention provides suchindividual injector action to an extent sufficient to providecomparatively smooth engine operation, good control of the number ofunpowered strokes, and generally effective utilization in practicalautomobile applications.

In yet another aspect of this invention, groups of fuel injectionsolenoids are sequentially energized under the control of semiconductorswitching devices such as transistors which are periodically biasedconductive in synchronism with operation of the engine. An electroniccontrol system including other semiconductor switches is provided whichis capable of preventing certain of the injector solenoids from beingenergized under certain conditions of operations. This disabling takesplace under the control of a pulse generator which may be controlled bythe operator or controlled automatically in response to an operatingcondition of the engine. The disabling control is arranged such that itis controlled by the pulse generator and by pulses developed by anengine driven pulse generator which also controls the sequence of firingof the groups of solenoid injectors.

IN THE DRAWINGS FIG. 1 is a schematic circuit diagram of one embodimentof a fuel injection system made in accordance with this invention;

FIGS. 2 through 5 are approximate and illustrative voltage waveformswhich illustrate graphically the operation of the system shown in FIG.1;

FIG. 6 is a schematic circuit diagram of an alternative form of thesystem shown in FIG. 1;

FIGS. 7 through 9 are approximate and illustrative voltage waveformswhich graphically illustrate the operation of the system shown in FIG.6;

FIG. 10 illustrates a modified circuit for the system of FIG. 1;

FIG. 11 is a schematic circuit diagram of still another modified fuelinjection system made in accordance with this invention;

FIG. 12 is a schematic circuit diagram of a variable frequency controlpulse generator which can be utilized in the various embodiments of thisinvention;

FIG. 13 illustrates a modified fuel injection system controlled by apulse counter arrangement; and

FIG. 14 illustrates a modified timing pulse generating arrangement forthe system of FIG. 13.

Referring now to the drawings and more particularly to FIG. 1, thereference numeral 10 designates an eight cylinder internal combustionengine for a motor vehicle. The fuel that is supplied to the engine iscontrolled by eight individual solenoid controlled injector valvesactuated by solenoids 10-1, 10-2, 10-3, 10-4, 10-5, 10-6, 10-7, and10-8, respectively. These injectors are located, for example, at therespective inlet valves for the eight engine cylinders in the order ofcylinder firing. Each solenoid, during energization, opens a fuel inletvalve, which discharges fuel from a source at constant pressure (notshown), so that the amount of fuel discharged in the region of eachinlet valve is determined by the duration of valve opening, which inturn is controlled by the time duration of energization of thecorresponding solenoid.

In the form of the fuel injection system shown in FIG. 1, the injectionsolenoids for the first four cylinders in the order of firing, areenergized in unison. The injection solenoids for the second fourcylinders, in the order of firing, are similarly energized in unison.The fuel thus discharged into each intake port adjacent but upstream theintake valve for each cylinder dwells in this location until theparticular cylinder begins an intake stroke. This dwell time can be nomore than one crankshaft revolution, since the four cylinders fueled inunison in each case are consecutively fired cylinders. During the intakestroke of each cylinder, the intake valve opens and the piston draws infuel and air, including the fuel previously discharged from the injectoron the prior injection pulse.

The engine is mechanically connected, for example, by a distributorshaft to an engine driven pulse generator designated by referencenumeral 12. This pulse generator can take various forms and might, forexample, be a cam driven switching device which has a square wave outputon line 14 as is illustrated in FIG. 1. It is preferred, however, thatthe engine driven pulse generator 12 be of the electromagnetic typewherein a pair of magnets having opposite poles on diametrically opposedpoints in relation to the shaft axis pass a pickup winding so as toinduce a voltage in the winding as the distributor shaft rotates. Thevoltage that is induced in the pickup coil is applied to adifferentiating circuit and to a flip-flop to produce the square wavevoltage shown in FIG. 1. One specific arrangement for developing thesquare wave voltage on line 14 is disclosed in U.S. Pat. applicationSer. No. 36.055, filed on May I l, l970 and assigned to the assignee ofthis invention.

The injector solenoids 10-1, 10-2, 10-3 and 10-4 are all connected withconductor 18 which in turn is connected to the positive side of a sourceof direct voltage 20 through a power supply conductor 22. The oppositeside of injector solenoids 10-1, 10-2 and 10-3 are connected to aconductor 24. An NPN transistor 26 has its collector-emitter circuitconnected between conductor 24 and ground and therefore betweenconductor 24 and the negative side of the source of direct current 20.With this arrangement it will be evident that when transistor 26 isbiased conductive the injector solenoids 10-1, 10-2 and 10-3 areconnected directly across the source of direct current 20 and thesesolenoids are therefore energized sufficiently to open the injectorvalves and supply fuel to the respective cylinders of the engine 10.

The injector solenoid 10-4, rather than being directly connected betweenconductors l8 and 24 is connected in series with a controlled rectifierdesignated by reference numeral 28. The gate of controlled rectifier 28is connected to conductor 18 through a capacitor 34. The capacitor 34 isconnected across the output terminals of a pulse generator 36 throughresistor 38. When the pulse generator 36 charges the capacitor 34 with avoltage of the proper magnitude and with the polarity indicated in FIG.1, gate current to the controlled rectifier 28 is opposed so as toprevent it from being biased to a conductive condition.

It will be appreciated that when transistor 26 is biased conductive, andassuming capacitor 34 does not have a prior charge preventing gatecurrent to the controlled rectifier 28, the voltage developed atconductor 18 will gate the controlled rectifier 28 conductive throughcapacitor 34. Under this condition of operation the solenoid 10-4 willbe energized in unison with solenoids 10-1, 10-2 and 10-3 each time thetransistor 26 is biased conductive.

The conduction of transistor 26 is controlled in synchronism withoperation of the pulse generator 12 by the signal on line 14 through asystem that will now be described. The signal on line 14 is applied to aSchmitt trigger designated by reference numeral 40 having outputterminals A and B. The output terminals A and B are connected withtransistors within the Schmitt trigger which are preferably connected inseries with resistors of predetermined values, whereby the voltageappearing between each of terminals A and B and ground alternatesbetween high and low levels. In other words, when the voltage at outputterminal A is high, the voltage at terminal B is at a lower level, andvice versa. The output terminal A is coupled to the base of an NPNtransistor 42 the collector of which is connected with power supplyconductor 22 by a resistor 44. The collector of transistor 42 is coupledto the base of NPN transistor 26. It will be appreciated that by theconnection of these transistors, transistor 26 will be biased conductivewhen transistor 42 is nonconductive and transistor 26 will be biasednonconductive when transistor 42 is conductive.

The bias voltage applied to the control transistor 42 is obtained fromterminal A of Schmitt trigger 40 and from an output terminal 56 of atransistor blocking oscillator designated by reference numeral 60. Thebase of transistor 42 is connected to output terminal 56 by conductors62 and 64 and resistor 66. It is seen that the output terminals A and Bof Schmitt trigger 40 are coupled to the blocking oscillator 60 and thisis done through differentiating circuits (not illustrated) whereby theoutput of Schmitt trigger 40 supplies a series of pulses to the blockingoscillator 60. Each time a pulse is supplied to the blocking oscillator60 from the Schmitt trigger, the output between junction 56 and groundof the blocking oscillator goes to a low value and this value ismaintained for the period of operation of the blocking oscillator. Thisperiod of operation is further controlled in response to enginetemperature and engine manifold pressure. This is indicated in FIG. 1 bythe lines 67 and 68 which indicate known methods of controlling thepulse period of the blocking oscillator in response to the engineconditions of this type. It should be pointed out here that the outputof the blocking oscillator is preferably an NPN transistor connectedbetween output terminal 56 and ground and therefore between conductor 64and ground.

The energization of injector solenoids 10-5, 10-6, 10-7 and 10-8 iscontrolled in a similar fashion to the energization of the otherinjector solenoids by complementary circuit elements which include apower output transistor 70 and an NPN control transistor 74. Thesetransistors are coupled to the power supply by resistor 45 asillustrated and the base of transistor 74 is connected with the B outputof Schmitt trigger 40 and to conductor 64 via resistor 76. The injector10-8 is connected in series with a controlled rectifier 80. A capacitor86 is connected between the gate of controlled rectifier and line 84,the latter being connected to power supply conductor 22 by conductor 85.The capacitor 86 is charged from pulse generator 36 through resistor 88.This capacitor operates in the same manner as capacitor 34 so as tostore the charge from pulse generator 36 and thereby block conduction ofcontrolled rectifier 80 until capacitor 86 is discharged.

Referring now back to the operation of transistors 42 and 74, it will beappreciated that the output voltages of the Schmitt trigger alternatebetween high and low levels as the Schmitt trigger is switched by thesignal on line 14. Assuming the output voltage on terminal A is at itslow value and that the blocking oscillator has been switched to a lowoutput level, the transistor 42 will be biased to a nonconductive state.This corresponds to time T of FIG. 2 where transistor 26 is illustratedbiased to a conductive condition. This comes about due to the fact thatthe nonconductive condition of transistor 42 causes a conductive statefor transistor 26 and at time T, a positive voltage will be applied toline 18 due to the conduction of transistor 26. Assuming that controlledrectifier 28 has not been disabled, injector solenoids -1, 10-2, 10-3and 10-4 will all be energized. This produces injection of fuel to fourcylinders of the engine. This injection will continue until a time whenthe blocking oscillator 60 switches from a low output state to a highoutput state. When this happens, transistor 42 is biased conductive,with the result that transistor 26 is biased nonconductive thusterminating current flow in the solenoids. This will occur at time Tshown in FIG. 2 and will occur in response to the duration of the onperiod of the blocking oscillator 60 as determined by engine operatingconditions.

This same analysis can be applied to the bias voltage applied to controltransistor 74. Thus, at time T the blocking oscillator 60 is set by asignal from Schmitt trigger 40 to its low output state and when a lowvoltage from the Schmitt trigger is simultaneously applied to controltransistor 74 it will be biased nonconductive with the result thattransistor 70 is biased conductive. At time T therefore, injectorsolenoids 10-5, 10-6, 10-7 and 10-8 will be energized for a perioddetermined by the pulse duration of blocking oscillator 60 and injectionis terminated at time T.,. This has assumed that no blocking signal wasapplied to disable controlled rectifier 80.

It will be appreciated from the foregoing that the transistors 42 and 74are alternately biased by Schmitt trigger 40 and by the output ofblocking oscillator 60. It will be further appreciated that injectioncan only occur when the proper simultaneous voltages are applied totransistors 42 and 74 from the blocking oscillator and the Schmitttrigger. It will be further appreciated that the voltage level set bythe Schmitt trigger will extend for the entire programmed injectionperiod, for example between times T, and T for transistor 42 and times Tthrough T for transistor 74, thus alternately enabling these transistorswhen the blocking oscillator has the proper output.

The operation of the controlled rectifiers 28 and 80, the pulsegenerator 36, and the associated circuitry is as follows. The pulsegenerator 36 produces a succession of pulses as illustrated by waveformD, FIG. 1, and at a controllable repetition rate. This generator may beof any desired construction, with a pulse producing capabilitysufficient to charge both capacitor 34 and capacitor 86 through therespective resistors 38 and 88 on each pulse to a sufficiently negativevoltage. to prevent gate current through the gate electrodes ofcontrolled rectifiers 28 and 80 to thereby prevent these controlledrectifiers from being biased to a conducting condition. The repetitionrate of the pulses is made variable between a minimum repetition ratecorresponding to the least number of unfueled piston strokes desired anda maximum repetition rate corresponding to the maximum number of suchunfueled strokes. Thus, for example, if the maximum number of unpoweredcylinder strokes is to be one-fourth of the total number of cylinderstrokes, the repetition rate of the pulse generator 24 is made equal toone pulse per crankshaft rotation. If, for example, the minimum numberof controlled unpowered piston strokes is to be one per 12 cylinderstrokes, then the minimum repetition rate of the pulse generator 36 isequal to one pulse per three crankshaft rotations.

Various forms of variable repetition rate pulse generators are known tothe art and may be used for the pulse generator 36. By way ofillustration, a multivibrator may be employed to produce anapproximately square wave of frequency determined by the feedback timeconstant of the circuit. The resulting wave may be differentiated andclamped to produce a series of positive pulses of repetition ratecontrollable by varying such feedback time constant or the square waveitself may be applied to the capacitors and controlled rectifiers wherea predetermined pulse width is desired.

The specific operation of the controlled rectifiers 28 and 80, the pulsegenerator 36 and the associated circuitry is as follows. The pulses D,FIG. 1, are applied to the SCR gate electrodes of controlled rectifiers28 and 80 in unison, thereby blocking energization of both solenoid 10-4and solenoid 10-8. The time constants of the capacitors 34 and 86 andtheir associated discharge circuits (including resistance 38 and 88) aresuch that this blocked condition remains for at least one crankshaftrotation. Before such crankshaft rotation is completed, one or the othersolenoid 10-4 or 10-8 is energized via the fuel injection pulsegenerator 12. At that time, the three unblocked injector solenoids ofthe injector group (10-1, 10-2 and 10-3, or 10-5, 10-6 and 10-7, as thecase may be) are actuated so as to supply fuel to their respectivecylinders. However, the blocked injector (10-4 or 10-8) does notoperate. Its cylinder, on subsequent inlet valve opening, draws in airfree of fuel and then discharges the same into the exhaust manifold.Thus the pulse from the pulse generator 36 has the effect of disablingthe fuel injection to the first one of injectors 10-4 and 10-8 whichwould otherwise discharge fuel to its respective cylinder.

When the energized injector solenoids are deenergized, as whentransistors 26 or go nonconductive, the current through the same issuddenly decreased, and a momentary voltage appears across the same inthe direction tending to continue such current flow. This voltage isapplied to capacitor 86 when the solenoids 10-1 to 10-4 are deenergizedthrough a circuit that includes conductor 24, conductor 89, capacitor86, conductors 84 and 85 and conductor 22 to line 18. When solenoids10-5 to 10-8 are deenergized, a voltage is supplied to capacitor 34through a circuit that includes conductor 91, conductor 18, conductor 22and conductors 85 and 84. The circuit is so designed that the magnitudeof this voltage is sufficient, when three or more injector solenoidshave a current interruption, to discharge the capacitor 34 or 86, as thecase may be, and reduce the voltage at the corresponding SCR controlelectrode to a value permitting the same to conduct in the event of aninjection pulse. Thus, the effect of actuation and subsequentdeenergization of either bank of injector solenoids is to clear theother bank for further injection by reducing the reverse bias charge ona capacitor 34 or 86. It is pointed out that each controlled rectifier28 or will be turned off where its associated transistor 20 or 70 goesnonconductive since at this time there is no voltage applied to itsanodecathode circuit. Moreover, the voltages induced in the solenoidswhen they are switched off tends to reverse bias II the anode-cathodecircuit ofa given controlled rectifier.

The operation of the system of FIG. 1 is illustrated in FIGS. 3 to 5,inclusive, for three specific different pulse repetition rates from thegenerator 36. In FIG. 3, the curve 3a illustrates on a time scale thesuccessive engine cylinder firing operations, with the wide pulsesindicating operation of injector solenoids 10-4 and 10-8. The respectivefiring times are identified by injector solenoid number. Curve 3b, FIG.3, shows the output pulses from the pulse generator 36. In theparticular repetition rate shown in FIG. 3 there is one pulse fromgenerator 36 for each l engine power strokes, as shown. Curve 3c, FIG.3, shows the actual engine power strokes under the conditions shown. Itwill be observed that the injector solenoids 10-8 and 10-4 are disabled,in accordance with which first follows each control pulse of curve 3b.It should further be noted that a variable number of power strokesseparate the respective non-powered strokes, the number varying fromseven to eleven in the illustrated operating condition.

FIG. 4 is like FIG. 3 but for the condition of one pulse from generator36 for each five cylinder power strokes. The curves 4a, 4b and 4c havethe same significance as curves 3a, 3b and 30, respectively, except thatthey pertain to the different repetition rate of pulse generator 36. Inthis case, the number of power strokes between successive non-powerstrokes varies from seven to three in the illustrated operatingcondition. Again, the non-power strokes are distributed randomly betweensolenoid injector 10-4 and solenoid injector 10-8.

FIG. 5 is like FIGS. 3 and 4 but for the condition of one pulse fromgenerator 36 for each 20 cylinder power strokes. The curves 5a, 5b and50 have the same significance as curves 3a, 3b and 30, respectively,except that they pertain to the different repetition rate of the pulsegenerator 36. In this instance, the number of power strokes betweensuccessive non-power strokes shown is nineteen and the non-power strokesare distributed between solenoid injector -4 and solenoid injector 10-8.

The overall action of the structure and circuitry above described withrespect to FIGS. 1-5 is to provide engine operation in the usual fashionexcept that there is normally one unpowered piston operation for eachpulse from the pulse generator 36. Normally, the greater the repetitionrate of this generator, the greater the number of such unpoweredoperations. A maximum occurs when both injector solenoid 10-4 andinjector solenoid 10-8 are disabled at all times, that is, the number ofpulses from generator 36 exceeds the number of possible operations ofinjector solenoids 10-4 and 10-8. The system thus makes possible thedischarge of air into the exhaust manifold at any selected rate, up toapproximately one-third of the total amount of spent air-fuel mixturedischarged into the exhaust manifold or one-fourth of the total enginedisplacement. Moreover, until the maximum is reached, there is asubstantially direct relation between the repetition rate of the pulsegenerator 36 and the number of unpowered cylinder operations per second.

In one application of the present invention, a catalytic afterburner isused to oxidize the unburned exhaust gas constituents. With the pulsegenerator 36 in operation at a predetermined pulse repetition rate,solenoids 10-4 and 10-8 are periodically disabled. The correspondingengine cylinders are not supplied with fuel from time to time and thendraw in air and discharge the same into the exhaust manifold and theninto a catalytic converter. Converter 15 preferably is of a type thatdoes not require an instantaneous supply of oxygen, but rather has someoxygen storage capability. Thus, when injector solenoids 10-4 and 10-8are disabled from time to time, the resultant momentary discharge intothe catalytic converter is remembered" and serves to supply oxygen forsubsequent periods of no air supply.

FIG. 6 is a diagram showing another form of the present invention whichis a modification of FIG. 1. The reference numerals in FIG. 6 identifyparts like similarly identified parts on FIG. 1 and FIG. 6 does notillustrate the entire system of FIG. 1. It is to be understood thattransistors 26 and 70, shown in FIG. 6, are controlled by a system thatis identical with the one shown in FIG. 1. In the construction of FIG.6, the respective controlled rectifiers 28 and each control the currentflow to two injector solenoids. That is, controlled rectifier 28, whendisabled (nonconducting), blocks current flow through both injectorsolenoid 10-2 and injector solenoid 10-4 and controlled rectifier 80,when nonconducting, blocks current flow through injector solenoid 10-6and injector solenoid 10-8.

FIGS. 7-9 are similar to FIGS. 35, respectively, but illustrate theoperation of the system of FIG. 6 rather than FIG. 1. As will be notedfrom FIGS. 7-9, the event of each control pulse from the pulse generator36 causes two injector solenoids to be blocked on the nextfuel-injecting pulse. That is, either injectors 10-2 and 10-4 as a pairare blocked or injectors 10-6 and 10-8 as a pair are blocked, dependingon which pair would otherwise first be energized. Since the cylinderpower strokes are determined by the spark timing, however, the times ofthe unfueled power strokes are spaced as shown in FIGS. 7-9. In theextreme case when the repetition rate of the pulses from generator 36 issufficient to block each of injectors 10-2, 10-4, 10-6 and 10-8, theengine operates on four cylinders with an equal time period betweensuccessive power strokes and therefore minimum roughness for the fourcylinder operating condition.

Referring now more particularly to FIG. 10, a disabling circuit which isa modification of the one shown in FIG. 1 is illustrated. In FIG. 10,the same reference numerals have been used as were used in FIG. 1 toidentify equivalent circuit elements in each embodiment and FIG. 10illustrates only a portion of FIG. 1, it being understood that theremainder of the system would be identical with that shown in FIG. 1.

In FIG. 10, the controlled rectifiers 28 and 80 rather than beingdisabled by the pulse generator 36 and associated capacitors 34 and 86are disabled by an NPN transistor designated by reference numeral 90 andcontrolled by pulse generator 36 through the flip-flop 102. The NPNtransistor 90 has its collector connected with a conductor 97, which inturn is connected to junctions 92 and 94. The junction 92 is connectedbetween the resistor 93 and a diode 96 whereas the junction 94 isconnected between the resistor 95 and diode 98. It is seen that thediodes 96 and 98 are connected with the gates of controlled rectifiers28 and 80. The cathodes of controlled rectifiers 28 and 80 are connectedwith a conductor 100 which in turn is connected with the emitter oftransistor 90.

From the foregoing it will be appreciated that when transistor 26 or 70is conductive, the associated controlled rectifier 28 or 80 will begated conductive through circuits that include, respectively, resistor93 and diode 96 and resistor 95 and diode 98. This has assumed that thetransistor 90 is biased nonconductive.

Whenever the transistor 90 is biased conductive (saturated), itscollector-emitter path shunts the gatecathode circuits of bothcontrolled rectifiers 28 and 80 and thereby prevents the controlledrectifiers from being gated to a conductive condition. This disables theassociated solenoid valve (104 or -8) to prevent fuel from beinginjected.

The conduction of transistor 90 is again controlled by pulse generator36 connected with a differentiator (not illustrated) which feeds pulsesto a flip-flop designated by reference numeral 102, each such pulseshifting the flip-flop to a condition that makes transistor 90conductive. The flip-flop 102 remains in this condition until restoredto the rest condition by the second subsequent actuation of Schmitttrigger 40. This is accomplished by pulser 105 which, in known manner,produces a restore pulse momentarily on line 107 when it is conditionedby a first disable pulse from pulse generator 36 and then actuated bythe next subsequent pulse on line 14, which (as shown in FIG. 1)actuates Schmitt trigger 40. The restore pulse is slightly delayed so asto hold flip-flop 102 in condition to maintain conduction of thetransistor 90 for a short time on the immediately following pulse online 14 so as to preclude conduction of controlled rectifier 28 orcontrolled rectifier 80, as the case may be, for an initial short timewhen conduction is otherwise called for.

Momentary deactivation or nonconduction of controlled rectifiers 28 or80, as the case may be, is held for the balance of the time injection iscalled for by the delayed disable voltage applied to their respectivecontrol electrodes from blocking oscillator 60 via conductor 62, FIG. 1.The capacitor 111 and resistor 113 delay the blocking voltage buildup onthe control electrodes of these controlled rectifiers for a timesufficient to cause these electrodes to lose control under normalconduction by these controlled rectifiers in response to conductionperiods of transistors 26 and 70. The time delay is slightly less thanthe delay of the restore pulse in line 107, so that when controlledrectifier 28 or 80 is nonconductive at the inception of an injectionperiod, it is held in that condition to the termination of thatinjection period.

The diodes 96 and 98 serve to prevent the saturation voltage oftransistor 90 from gating controlled rectifiers 28 and 80 on whentransistor 90 is fully conductive. Zener diodes could be used for thispurpose if desired.

FIG. 11 is a schematic circuit diagram ofa fuel injection systemincorporating another modification of the present invention. In thesystem of FIG. 11, the reference numeral 200 has been used to identify afuel injection pulse generator. The block 200 represents the controlsystem shown in FIG. 1 which triggers transistors 26 and 70 on" andoff". These transistors are connected with lines 234 and 242 so thatpulses of positive voltage, designated by the letters B and C in FIG.11, are sequentially applied to lines 234 and 242. In other words, inthe system of FIG. 11 the transistors 26 and 70, with their associatedinput network, would be connected between a source of direct current andconductors 234 and 242 to apply the direct current pulses to lines 234and 242 in synchronism with the engine.

In the arrangement of FIG. 11, the injector solenoids 10-1, 10-2 and10-3 are energized from source 202 through the collector-emitter path oftransistor 201. Similarly, injector solenoid 10-4 is energized fromsource 202 through the collector-emitter path of transistor 204,injector solenoids 10-5, 10-6 and 10-7 are energized through thecollector-emitter space path of transistor 206 and injector solenoid10-8 is energized through the collector-emitter space path of transistor208. The bases of transistors 201 and.204 are connected via resistances210 and 212, respectively, to line 242. As described above, line 242 hasa positive voltage pulse on alternate crankshaft rotations, indicateddiagrammatically at 0, 2, 4, 6, etc., in curve B, FIG. 11. The bases oftransistors 206 and 208 are connected via resistances 214 and 216,respectively, to line 234 of fuel injection pulse generator 200 whichhas a positive voltage pulse on the intermediate alternate crankshaftrotations as shown in curve C, FIG. 11.

Under unimpeded operation of the transistors '204 and 208, the system ofFIG. 11 energizes solenoids 10-1, 10-2, 10-3 and 10-4 in unison on theeven numbered rotations of the crankshaft, and energizes solenoids 10-5,10-6, 10-7 and 10-8 in unison on the odd numbered rotations of thecrankshaft. As above described, the fuel injection pulse generator 200produces pulses of correct duration to inject the proper amount of fuelon each cylinder operating cycle so that the engine operates as desired.

In the circuitry of FIG. 11, each of the injector solenoids 10-4 and10-8 is selectively disabled through the action of the correspondingcapacitor 218 and 220, re spectively. As shown, these capacitors areconnected between the base of the corresponding transistor 204 or 206,respectively, and ground and are both connected to the output of pulsegenerator 224. Additionally, the collector-emitter paths of transistors222 and 226 are connected across capacitors 218 and 220, re spectively.The base of the transistor 222 is connected through resistance 228 toground and via diode 232 and capacitor 230 to the output terminal 234 ofthe fuel injection pulse generator 200. Similarly, the base oftransistor 226 is connected by resistance 236 to ground and via diode240 and capacitor 238 to the other output terminal 242 of the fuelinjection pulse generator 14.

The above described circuitry operates as follows. When the pulsegenerator 224 produces a pulse, as shown in waveform D, the same isapplied to the capacitors 218 and 220 in parallel. The pulse is ofnegative polarity, as indicated by waveform D. The circuit constants arechosen to cause these capacitors to be charged sufficiently to precludeinjector solenoid energization by transistors 204 and 208 in the eventof operating pulses on lines 2 42 and 234. Injector solenoids 10-4 and10-8 are thus temporarily disabled. When the first injector operatingpulse occurs, the corresponding injector 10-4 or 10-8, as the case maybe, remains deenergized so that the corresponding engine cylinder is notfueled on its next power stroke. The same injector operating pulse,however, serves to discharge the opposite capacitor 220 or 228 as thecase may be via the capacitor 238, rectifier 240 and resistance 236 inthe case of capacitor 220 and the capacitor 230, rectifier 232 andresistance 228 in the case of capacitor 218. Thus each pulse of thepulse generator 224 gives rise to one miss" of injector -4 or injector10-8, depending on the timing of the pulse, except of course when thepulse repetition rate is so great that both injectors 10-4 and 10-8 aredisabled.

More particularly, the action of the capacitor 238, rectifier 240 andresistance 236 in discharging capacitor 220 is as follows. Assume thatcapacitor 220 has a negative charge due to a prior pulse from source224.

The transistor 226 does not conduct to drain off this charge with noforward biasing pulse from the pulse generator 200. Thus, when thetransistor 208 is disabled and there is substantial charge on capacitor220 at the instant a pulse occurs on line 242 even at low engine speed.Since the voltage across capacitor 238 does not instantaneously changewhen the pulse occurs on line 242, and since the rectifier 240 is poledin a direction to carry charging current to capacitor 238 when thepositive pulse appears on line 242, the positive pulse at line 242appears as a positive pulse across resistance 236 and at thebase-emitter of transistor 226, rendering the collector-emitter circuitpath of transistor 226 conductive. The values of capacitor 238,resistance 236 and the characteristics of transistor 226 are so chosenin relation to the negative charge existing on the capacitor 220 thatthis action serves to leave a charge on capacitor 220 such thattransistor 208 becomes conductive when a positive pulse subsequentlyappears on line 234. In other words, transistor 208 is now conditionedfor action in response to a pulse on line 234. The net action,therefore, is for the positive pulse from generator 200, appearing online 242, to discharge the capacitor 220 if it has been previouslycharged from pulse generator 224. After this action has occurred, theresidual charge on capacitor 238 drains off via resistance 244.

In the case of capacitor 218, the event of a positive pulse on line 234changes the charge if it be a negative value blocking the conduction oftransistor 204 to a value that permits such conduction when a subsequentpulse on line 242 occurs. This discharge of capacitor 218 occurs throughthe collector-emitter space path of transistor 222 which is madeconducting by the positive voltage appearing on its base when the pulseoccurs on line 234. This positive pulse is communicated to the base oftransistor 222 by capacitor 230 and diode 232. Capacitor 230subsequently discharges through the resistance 246.

The circuit of FIG. 11 operates to give generally the same blockingaction of solenoid injectors 10-4 and 10-8 as the circuit of FIG. 1. Thediagrams of FIGS. 3-5 apply to the action of the circuit of FIG. 12 inthe same respect as they do to the action of the circuit of FIG. 1.

If desired, solenoid injector 10-2 may be connected in parallel withsolenoid injector 10-4, FIG. 11, and injector solenoid 10-6 may beconnected in parallel with injector solenoid 10-8. In this case, thecircuit action is substantially as described above with regard to FIG. 6and FIGS. 79 inclusive. That is, the occurrence of a negative pulse fromgenerator 224 will then cause two subsequent unfueled cylinder powerstrokes.

FIG. 12 shows a system for controlling the output frequency of thedisabling pulse generators of FIGS. 1, 6, 10 or 1 1 by an enginethrottle control as used on a vehicle so as to automatically vary thenon-powered strokes in accord with throttle position. There is shown at300 a conventional operator foot pedal with is depressed for increasedengine power and released to decrease engine power. This pedal is pinnedat 301 to the link 302 which is pivoted at 304 to arm 306a of crank 306.The crank 306 is unitary with the shaft 308 which is supported bysuitable bearings (not shown) for rotation about a fixed axis. The otherarm 306b of crank 306 is pivoted at 310 to the link 312. At 314 the link312 is pivoted to the crank am 316 which in turn is mounted on the shaftof the throttle valve 318 so as to open and close throttle valve 318 andthereby vary the air flow to the engine 10 through the inlet pipe 320.Throttle return spring 322 urges the throttle to closed position. Thuswhen the foot pedal 300 is depressed, the throttle valve 318 is openedagainst the bias of spring 322 to admit more air to the engine andincrease the engine power.

The crank 306 is unitary with and thus rotates the shaft 308. This shaftalso carries a potentiometer contact arm shown diagrammatically at 324.This arm makes electrical contact with the fixed resistance element 326as shown. The shaft 308 and hence the arm 324 are grounded as indicated.The line 328 is connected to one end of the resistance element 326 so asto provide increasing resistance in relation to the ground terminal asthe foot pedal is depressed. This resistance is connected to a suitablepulse generating circuit 340 so as to produce pulses having repetitionrate that decreases as the resistance increases in response to footpedal depression. The specific circuit illustrated in FIG. 12 is of thetype shown and described at pages 337338 of the General ElectricTransistor Manual (7th Ed., 1964), which is one of the various circuitsthat can be used for pulse generator 36, FIGS. 1, 6 and 10, or pulsegenerator 224, FIG. 11. This circuit includes a pair of transistors 333and 335 connected as a bistable multivibrator and a unijunctiontransistor 337 connected to control the time period from one conditionto the other, all as described in the above manual. The output of thiscircuit is a substantially rectangular wave, as shown at E, FIG. 12.This is differentiated by capacitor 330 and resistance 332 to producethe alternate positive and negative pulses as shown at F, FIG. 12. Thenegative pulses are blocked by diode 334, FIG. 10, so as to produce thepositive pulses, as indicated at G, which is the desired output of pulsegenerator 36, FIGS. 1, 6 and 10. The repetition rate of these pulses isdetermined by the frequency of the wave E, which in turn depends on thevalue of resistance 326 in the circuit and hence the position of thethrottle control pedal 300.

If negative pulses are desired, as in the case of the apparatus of FIG.11, the diode 334 is reversed so as to block the positive pulses, thusproviding the outputt waveform D of pulse generator 224, FIG. 11.

The relation between the pulse repetition rate and the throttle positionmay be selected by appropriately tapering the fixed resistance element326. Beyond a predetermined throttle position, for example, it may bedesirable to run the engine with all cylinder operations fueled whichcan be done by terminating resistance 326 as at 326a, FIG. 12, and thusdisabling the pulse generator.

The apparatus of FIG. 12, when used with that of FIGS. 1, 6, 10 or 11,or the equivalent, provides an increased rate of unfueled cylinderoperation as the foot pedal 300 is released and the throttle closes. Itis thus useful where it is desired either to have progressively fewercylinders fueled as the throttle pedal is released so as to keep thosecylinders operating under the most favorable and eff cient conditions ofcombustion or to have progressively greater proportion of air in theexhaust system as the throttle pedal is released.

FIG. 13 is a modified arrangement for disabling certain of the fuelinjectors in timed relation to engine operation. It is to be understoodthat the pulse generating arrangement of FIG. 13 can be substituted forthe pulse generator 36 of FIGS. 1, 6 and 10 or generator 224, FIG. 11.For convenience of illustration, the pulse generating arrangement isdisclosed as controlling the system of FIG. 10 and in this regard thetransistor 90 is shown in FIG. 13 connected with conductors 97 and 100,it being understood that this transistor will control the fuel injectionsystem of FIG. 10.

In FIG. 13, the reference numeral 400 is used to designate a source offuel injection pulses which occur, for example, at time periods T, and Tshown in FIG. 2. This source of pulses can be obtained as one examplefrom the input line 14 to the Schmitt trigger 40 where they aredifferentiated and connected with suitable diodes to eliminate theunwanted pulses. In other words, a differentiator (not shown) isconnected to conductor 14 and provides a series of pulses shown in FIG.13 which occur at the beginning of each injection period.

The conductor 402 which has injection or timing pulses applied theretois connected with a switch designated by reference numeral 404. Thisswitch is closed whenever it is desired to disable certain of the fuelinjector solenoids and the switch can be operated, or ex ample, throughlinkage connected with accelerator pedal 300 such that the switch onlycloses over a predetermined range of movement of accelerator pedal 300.Alternatively, the switch 404 could be closed over a predetermined rangeof speed of the engine by a centrifugal device (not illustrated) whichwould respond to engine speed.

When switch 404 is closed, the system of FIG. 13 is set to provide acontrolled disabling of certain fuel injectors of the system. Thus, whenswitch 404 is closed, injection pulses are applied to a conductor 406.The conductor 406 feeds pulses to a pulse counter which is generallydesignated by reference numeral 416. Although the counter 416 can take awide variety of forms, it is disclosed specifically herein as what isknown in the art as a storage counter. This type of counter is disclosedat pages 706-713 of the book entitled Pulse, Digital and SwitchingWaveforms, Millman and Taub, McGraw-Hill Book Company (1965). Thiscounter includes capacitors 418 and 420 and diodes 422 and 424. When aseries of pulses is applied to the storage counter 416 the capacitor 420is progressively charged stepwise by each pulse input to the counter sothat the voltage attained by capacitor 420 is a function of the numberof pulses that have been applied to the counter.

The capacitor 420 is connected with the emitter E of a unijunctiontransistor designated by reference numeral 426. One of the baseelectrodes B, of the unijunction transistor is connected with resistor428 and with a conductor 430 which is connected to the set terminal of aflip-flop designated by reference numeral 432. The base electrode B ofthe unijunction transistor is connected in series with a resistor 434and this resistor is connected in series with a resistor 436. Theresistor 436 is connected in series with a source of direct current 438,the negative terminal of which is connected to one side of resistor 428so that the voltage of direct current source 438 is applied across thebase electrodes of the unijunction transistor and the magnitude of thisvoltage is controlled by adjusting variable resistor 436. The resistor436 and direct current source 438 provide a means for adjusting thefiring point of the counter and hence the number of counts beforeactuation. It is hereinafter termed a counter control which isdesignated in FIG. 13 by reference numeral 440.

The unijunction transistor in this circuit operates as a variablevoltage discharge switch in that the unijunction transistor will conductbetween its emitter E and base B to discharge capacitor 420 throughresistor 428 whenever it attains a predetermined net space-path voltage.This net space-path voltage is determined by the charge on capacitor 420and the setting of resistance 436. This means that the counter 416 willdevelop a voltage across resistor 428 which is applied to flip-flop 432whenever a predetermined number of pulses have been applied to thecounter 416.

Resistor 436 controls the firing point of the counter 416. It can beadjusted so that the counter can be set to be actuated for differentpredetermined number of counts. It is known that the voltage at whichthe unijunction transistor will conduct between emitter E and base B, isa function of the voltage applied across the base terminals B and 13,.This voltage is adjustable by varying resistor 436. Thus, the countercontrol 440 can be adjusted to vary the number of counts required beforea pulse of voltage is developed across resistor 428. It will, of course,be appreciated by those skilled in the art that the variable voltageapplied to base electrodes B and B, could be provided by other means,for example a tachometer generator driven by the engine where it isdesired to vary the number of counts as a function of engine speed. Inaddition, it will be appreciated by those skilled in the art that thenumber of counts for counter 416 could be varied by any other suitableautomatic programming means which is capable of varying the voltagebetween base electrodes B and B,.

The summarize the operation of the system of FIG. 13 as thus fardescribed, it is seen that whenever switch 404 is closed the injectionpulses are sequentially applied to the counter 416. When the counter 416has accepted the predetermined count it develops a voltage acrossresistor 428 which is applied to flip-flop 432. The output of flip-flop432 is applied to a conductor 442 and is of such a polarity as to biastransistor conductive. As previously pointed out in conjunction withFIG. 10, this will result in certain of the fuel injector solenoids tobe disabled to prevent fuel injection by these injectors.

When the counter 416 attains its predetermined count the capacitor 420discharges as pointed out above. The discharge of capacitor 420automatically resets the counter 416 for a new counting cycle and thecounter will again count the .pulses applied to line 406 providingswitch 404 is still closed to initiate another disable event.

The flip-flop 432 has a reset terminal R that is connected to conductor406 by a conductor 435. Each time a pulse from source 400 is applied tothe R terminal of flip-flop 432, the flip-flop is reset (if it is in theset state) to a state where transistor 90 is biased nonconductive withthe result that the fuel injectors are no longer disabled. The periodicapplication of injection pulses to reset terminal R while counter 416 iscounting does not change the state of flip-flop 432 after the flipflophas been shifted from its set state to its reset state by the firstreset pulse. Therefore, the transistor 90 remains biased non-conductiveso that fuel injection is not inhibited as the counter 416 is counting.

When the counter 416 attains its predetermined count, the flip-flop 432changes to its set state since a pulse is applied to set terminal S fromthe counter. Transistor 90 is now biased conductive to prevent fuelinjection by certain of the injectors. This disabling of certain fuelinjectors (for example, 10-4 or 10-8) continues until the flip-flop 432is reset by the next pulse on line 434 from pulse source 400.

From the foregoing it will be appreciated that as long as switch 404 isclosed, certain of the fuel injectors will be periodically disabled atthe end of each counting cycle of counter 416. The rate of disablingwill be a function of crankshaft revolutions and the setting of thecounter control 440.

Referring now more particularly to FIG. 14, a modified source of pulseswhich could be substituted for the pulse source 400 in FIG. 13 isillustrated. In FIG. 14 a pulse generator 500 is provided which includespermanent magnet 502, a pickup coil 504 and a toothed wheel 506 which isconnected with the distributor shaft and therefore rotates insynchronism with the crankshaft of the engine. The pulse generator 500can be of a type shown in the U.S. Patent to Falge No. 3,254,427 whichillustrates in detail the toothed wheel, permanent magnet and pickupcoil. This pulse generator can also be used to control the ignitionsystem of the engine and an alternating voltage is induced in pickupcoil 504. This voltage is rectified by a diode 508 and the pulse outputis then applied to a monostable multivibrator 510 to provide the shortsquare wave pulses designated by reference numeral 512 in FIG. 14. Thepulses 512 would then be applied to counter 416 and reset terminal R offlip-flop 432 in FIG. 13. When using the system of FIG. 14, actual powerpulses are counted since the pulses 512 determine the point in time atwhich a spark plug is fired. It, of course, will be appreciated thatwhether the pulses are fuel injection pulses or ignition timing pulses,they are in each case developed in synchronism with rotation of thecrankshaft of the engine and occur at predetermined angular positions ofthe crankshaft.

In the foregoing description, the fuel injection system is of the typehaving two banks of injectors with the injectors of each bank energizedin unison. The invention is equally applicable to systems wherein theinjectors are energized in more than two banks, or. are individuallyenergized. In such instance, the reset lines 89 and 91, FIG. 1, forexample, would each be connected to the solenoid for a cylinder that isnot subject to blocking by a controlled rectifier, such as solenoids10-2 and 10-6, respectively.

The particular cylinders selected for disabling of the fuel injectionshould be a group having uniform time spacings of their power strokes,such as the fourth and eighth in an eight-cylinder engine, or thesecond, fourth, sixth and eighth in such an engine. It will beunderstood, of course, that modifications and alternative constructionsmay be made without departing from the true spirit and scope of thepresent invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, a multi-cylinder internal combustion engine-having afirst cylinder that executes power strokes during the first half of acrankshaft rotation period and a second cylinder that executes powerstrokes during the second half of said crankshaft rotation period, andfuel intake valves for the cylinders, respectively;

electrically energizable fuel injectors for said cylinders,respectively, and adapted when energized to discharge fuel adjacent thefuel intake valves, respectively, for induction into the cylinders;voltage pulse developing means synchronized with operation of saidengine operable to energize the fuel injectors for the first cylindermomentarily during the first half of crankshaft rotation and to energizethe fuel injector for the second cylinder momentarily during the secondhalf of crankshaft rotation;

first and second electrically controlled disabling means effective todisable the fuel injectors, respectively, said disabling means beingactuated in unison and in response to a predetermined control eventwhereby a fuel injector is disabled in the event a disabling means isenergized at the time of occurrence of a pulse from said voltage pulsedeveloping means;

and means effective when one injector has been deenergized to reset theother for undisabled injection.

2. In combination, a multi-cylinder internal combustion engine havingcylinders that execute power strokes in sequence, fuel intake valves forthe cylinders, respectively, and a fuel intake manifold definingpassages for the intake of airfuel mixture to said cylinders,respectively;

electrically energizable fuel injectors for said cylinders,respectively, and adapted when energized to discharge fuel to saidintake manifold adjacent the fuel intake valves, respectively; pulsedeveloping means synchronized with operation of said engine forenergizing the fuel injectors, said pulse developing means beingeffective to alternately energize sequentially each of two fuelinjectors at differing times in the engine operating cycle;

and electrical control means effective to disable in unison said twofuel injectors, said control means being actuated on a predeterminedcontrol event and being restored to inactive condition in response to achange in voltage of said pulse developing means, whereby saidpredetermined control event is effective to interrupt fuel for a limitedtime less than a complete engine operating cycle when said control eventhas occurred at the time a pulse is developed by said pulse developingmeans.

3. A fuel injection system for controlling the supply of fuel to aninternal combustion engine comprising;

a plurality of electrically energizable fuel injectors for controllingthe injection of fuel to said engine; means for developing a series ofvoltage pulses in timed relation with operation of said engine; meansfor applying said pulses sequentially to first and second fuel injectorswhereby said fuel injectors are alternately energized in sequence toinject fuel into said engine under one condition of operation;

first and second electrically controlled disabling means connected,respectively, with said first and second fuel injectors for preventingthe injection of fuel by a respective fuel injector when a disablingmeans is actuated;

a source of disabling control pulses;

means connecting said source of disabling control pulses to said firstand second disabling means whereby said electrically controlleddisabling means are energized in unison to prevent energization of aninjector that has a voltage pulse applied thereto;

and means responsive to said voltage pulses for resetting said disablingcontrol means.

4. A fuel injection system for an internal combustion engine comprising;

first and second fuel injectors each having a solenoid which whenenergized sufficiently opens a fuel injector valve to supply fuel to aninternal combustion engine;

a source of direct current;

first and second semiconductor switch means connected, respectively,with said source of direct current and with said first and secondsolenoids for energizing said solenoids when a respective semiconductorswitch means is biased to a conductive c0ndition;

means operable in timed relation with said engine for alternatelybiasing said first and second semiconductor switch means conductive forpredetermined lengths of time;

third and fourth semiconductor switch means connected, respectively, inseries with said first and second fuel injector solenoids;

means for causing said third and fourth semiconductor switch means to bebiased alternately conductive, respectively, as said first and secondsemiconductor switch means are biased alternately conductive;

and control means coupled to said third and fourth semiconductor switchmeans for simultaneously and periodically preventing said third andfourth semiconductor switch means from being biased conductive, wherebyeach associated fuel injector solenoid is prevented from being energizedwhen a respective first or second semiconductor switch means is biasedconductive.

1. In combination, a multi-cylinder internal combustion engine having afirst cylinder that executes power strokes during the first half of acrankshaft rotation period and a second cylinder that executes powerstrokes during the second half of said crankshaft rotation period, andfuel intake valves for the cylinders, respectively; electricallyenergizable fuel injectors for said cylinders, respectively, and adaptedwhen energized to discharge fuel adjacent the fuel intake valves,respectively, for induction into the cylinders; voltage pulse developingmeans synchronized with operation of said engine operable to energizethe fuel injectors for the first cylinder momentarily during the firsthalf of crankshaft rotation and to energize the fuel injector for thesecond cylinder momentarily during the second half of crankshaftrotation; first and second electrically controlled disabling meanseffective to disable the fuel injectors, respectively, said disablingmeans being actuated in unison and in response to a predeterminedcontrol event whereby a fuel injector is disabled in the event adisablinG means is energized at the time of occurrence of a pulse fromsaid voltage pulse developing means; and means effective when oneinjector has been deenergized to reset the other for undisabledinjection.
 2. In combination, a multi-cylinder internal combustionengine having cylinders that execute power strokes in sequence, fuelintake valves for the cylinders, respectively, and a fuel intakemanifold defining passages for the intake of air-fuel mixture to saidcylinders, respectively; electrically energizable fuel injectors forsaid cylinders, respectively, and adapted when energized to dischargefuel to said intake manifold adjacent the fuel intake valves,respectively; pulse developing means synchronized with operation of saidengine for energizing the fuel injectors, said pulse developing meansbeing effective to alternately energize sequentially each of two fuelinjectors at differing times in the engine operating cycle; andelectrical control means effective to disable in unison said two fuelinjectors, said control means being actuated on a predetermined controlevent and being restored to inactive condition in response to a changein voltage of said pulse developing means, whereby said predeterminedcontrol event is effective to interrupt fuel for a limited time lessthan a complete engine operating cycle when said control event hasoccurred at the time a pulse is developed by said pulse developingmeans.
 3. A fuel injection system for controlling the supply of fuel toan internal combustion engine comprising; a plurality of electricallyenergizable fuel injectors for controlling the injection of fuel to saidengine; means for developing a series of voltage pulses in timedrelation with operation of said engine; means for applying said pulsessequentially to first and second fuel injectors whereby said fuelinjectors are alternately energized in sequence to inject fuel into saidengine under one condition of operation; first and second electricallycontrolled disabling means connected, respectively, with said first andsecond fuel injectors for preventing the injection of fuel by arespective fuel injector when a disabling means is actuated; a source ofdisabling control pulses; means connecting said source of disablingcontrol pulses to said first and second disabling means whereby saidelectrically controlled disabling means are energized in unison toprevent energization of an injector that has a voltage pulse appliedthereto; and means responsive to said voltage pulses for resetting saiddisabling control means.
 4. A fuel injection system for an internalcombustion engine comprising; first and second fuel injectors eachhaving a solenoid which when energized sufficiently opens a fuelinjector valve to supply fuel to an internal combustion engine; a sourceof direct current; first and second semiconductor switch meansconnected, respectively, with said source of direct current and withsaid first and second solenoids for energizing said solenoids when arespective semiconductor switch means is biased to a conductivecondition; means operable in timed relation with said engine foralternately biasing said first and second semiconductor switch meansconductive for predetermined lengths of time; third and fourthsemiconductor switch means connected, respectively, in series with saidfirst and second fuel injector solenoids; means for causing said thirdand fourth semiconductor switch means to be biased alternatelyconductive, respectively, as said first and second semiconductor switchmeans are biased alternately conductive; and control means coupled tosaid third and fourth semiconductor switch means for simultaneously andperiodically preventing said third and fourth semiconductor switch meansfrom being biased conductive, whereby each associated fuel injectorsolenoid is prevented from being energized when a respective first orsecond semiconductor switch means is biased coNductive.